Speaker
Description
In the FLNR JINR at the kinematic separator SHELS the new neutron-deficient isotope $^{249}$No was synthesized for the first time in the complete fusion reaction $^{204}$Pb($^{48}$Ca,3n)$^{249}$No. Using the GABRIELA detection system, the new isotope was identified through genetic correlations with the known daughter and granddaughter nuclei $^{245}$Fm and $^{241}$Cf , and new activity has an energy E$_{\alpha}$ = 9129 keV and half-life T$_{1/2}$=38.3(2.6) msec. An upper limit of 0.2% was evidenced for the fission branch of $^{249}$No. Correlation events of the $^{249}$No alpha activity with subsequent alpha decays of energy 7728(20) keV and half-life T$_{1/2}$=$0.94_{-0.29}^{+0.76} min $ provided a firm measurement of the electron-capture branch of $^{245}$Fm to $^{245}$Es. The production cross section was found to be σ(3n)=0.47(3) nb at a mid-target beam energy Elab = 222.2 MeV, which corresponds to the maximum of the calculated excitation function. The excitation function for the 1n, 2n and 3n evaporation channels was measured.
